Cellulose rendered water repellent by application of a cationic beta-iron oxide hydrosol



United States Patent 3,335,726 CELLULOSE RENDERED WATER REPELLENT BY APPLICATION OF A CATIGNIC BETA-IRON 0X- IDE HYDROSQL Charles J. Conner, New Urleans, lLa., assignor to the United States of America as represented by the Secretar-y of Agriculture No Drawing. Filed Aug. 13, 1965, Ser. No. 480,827 1 Claim. (Ci. 117-1355) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the deposition of cationic iron oxide on anionic cellulosic material. More specifically, this invention refers to the treatment of cellulosic material with aqueous colloidal solutions of cationic betaferric oxide, referred to as a positive iron oxide hydrosol (Fe O thereby rendering the said cellulosic material resistant to Wetting with water.

This facile and inexpensive application is suitable for imparting water repellency to cellulosic materials which do not require a pure-White coloration, such as kraft paper bags, wrapping paper and cartons, building materials, fiber board, insulating materials, canvassing material, cotton textiles, etc.

In the prior art J. W. Mellors Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. XIII, Fe (Part 2), pp. 831-836 (-Iron Hydrosols) discusses the iron and iron oxide compounds and shows the preparation and physical characteristics of the various forms, among which the beta-form of the iron oxide is described. No mention of how these substances can be utilized is made. In the course of other investigative work I have unexpectedly discovered that the beta-form of iron oxide adheres to cellulosic material and in so doing imparts to the cellulosic material a water repellency which is durable; furthermore, I have learned that this water repellency can be imparted to the said cellulosic materials by the simple process of impregnating the said cellulosic material with an aqueous suspension of low concentration of beta-iron hydrosol at room temperature, prepared from the aqueous hydrolysis of ferric chloride solution, washing the impregnated material to remove the hydrogen chloride formed when the anionic cellulosic material comes in contact with the cationic beta-iron hydrosol, and drying the impregnated material in the oven at 90 to 100 C. or at room temperature. Spray rating about from 50 to 70 have been accomplished in my investigations, and the materials which have been included in these investigations include paper, canvas, print cloth, yarns, and non-woven cotton. The degree of water repellency obtained or imparted to the finished material is dependent on the anionic character of the cellulosic material being impregnated, the concentration of the ferric hydrosol used to produce the add-on, and the contaminants of the water used.

I have found that normal iron oxides alone cannot impart water repellency, however, the iron oxide of my invention does impart water repellency to the treated cellulosic materials, and is that form of ferric oxide with cationic character as deposited from a hydrosol, and for that reason reacts with the cellulose which normally is of anionic character, possibly forming the covalent bond of the iron oxide and the cellulosic material. The ferric chloride in aqueous solution forms beta-iron oxide immediately upon heating the solution to about 85 to 90 C., which remains as a stable colloidal system at room temperatures.

3,385,726 Patented May 28, 1958 Theoretically, the iron oxide could be contributed by substances other than ferric chloride, but -I prefer to use the ferric chloride of formula weight 270.2. More specifically I prefer to use the hydrated ferric chloride (FeCl -6H O) of formula weight 270.2 in aqueous solutions of about from 1.0% to 5.0% concentration, by Weight. Even the lower concentrations impart the desired degree of water repellency. The higher concentrations impart too dark a coloration, which in itself is not bad for select applications of water repellency treatments.

The chemical literature has long referenced the preparation of uncommon oxides of iron, one of which has been designated as beta-iron oxide. The beta-iron oxide can be produced by slowly heating aqueous solutions of select ferric salts, such as ferric chloride or ferric acetate, to about to C. for period of time about from 2 to 5 minutes.

A significant feature of my present invention is that no alkali is required in order to precipitate the iron oxide on the cellulosic material. The formation takes place apparently by hydrolysis, at a pH about from 2.5 to 6.5. However, the pH is relative to the concentration of the FeCl -6H O and water. This feature of the process contributes to the novelty of imparting water repellency by this inexpensive treatment.

The cellulosic material is made to receive a uniform deposit of the oxide by merely dipping or padding in conventional equipment containing the colloidal solution of the beta-ferric oxide hydrosol at room temperatures. The deposit so formed on the cellulosic material cannot be removed by water nor leaching, and when the treated material is dried, it demonstrates a notable water repellency. The process is readily carried out in conventional equipment, is inexpensive, is nontoxic, and can find industrial feasibility in the treatment of materials and articles such as kraft paper bags, wrapping paper, envelopes, tarps, building materials, cotton textiles, etc. Also, it can be employed for the treatment of disposable curtains, water hose, and rainwear.

For example, a quantity of print cloth was treated with the beta-iron oxide hydrosol to give a low 0.2% Fe O content, and was found to have a 50 spray rating. Beads of distilled water rolled freely across the surface of this treated cloth; identical add-on on paper towelling was found to have very similar results, the water beads rolled olf readily.

The process of application which is part of my invention can be carried out in a continuous system, where the cellulosic material is dipped and nipped, water washed and oven dried, in a manner common to the textile and paper industries.

The following examples are set forth to illustrate but not to limit the scope of this invention.

Example 1 A 3% Fe O hydrosol was prepared by dissolving 3 gm. of ferric chloride (FeCl -6H O) in 97 gm. of distilled water and heating the solution on a hot plate for 4 min utes at 85 C. to eifect the conversion of the ferric chloride to beta-iron oxide hydrosol. The hydrosol was readily detected by the formation of a colloidal system which is opaque to reflected light and shows a deep red color by transmitted light. The hydrosol solution was allowed to cool to room temperature .(about 25 C.), at which temperature the hydrosol showed no precipitation, and was stable for cellulosic textile applications.

Example 2 A second 3% Fe O hydrosol was prepared by the process of Example 1, however the solution was heated for 15 minutes at 85 C.

Example 3 A 2% Fe O hydrosol was prepared by dissolving 2 gm. of the ferric chloride of Example 1 in 98 gm. of distilled water. The process and conditions of Example 1 were repeated, and similar results were observed.

Example 4 A 1% Fe O hydrosol was prepared by dissolving 1 gm. of the ferric chloride of Example 1 in 99 gm. of distilled water. The process and conditions of Example 1 were repeated, and similar results were observed.

Example 5 Small swatches of cotton printcloth, poplin, broadcloth, and scoured duck, also some absorbent paper towelling, were immersed in the hydrosol solutions of Examples 1, 2, and 3, at room temperatures, for periods of time about from 0.5 to minutes whereby the colloidal particles are rapidly attracted to the cellulosic materials, producing orange-yellow to orange colorations in the various materials so treated. The treated materials were rinsed in distilled water and/ or in cold tap water for periods of time up to several hours, and found to retain their uniform coloration imparted by the deposition of the Fe O Example 6 The rinsed samples from Example 4 were investigated in the following manner. The samples were divided into two groups, the one group was oven dried for 3 minutes at 103 C., and allowed to equilibrate at room temperature C.) from the dry side, while the other group was allowed to dryand equilibrate-from the wet side at room temperature. Water repellency was noted in all the treated materials when a bead was formed on the surface while the treated sample was held in a horizontal position. The samples were further tested for water repellency while each sample was held at 45 to the horizontal plane. Water repellency was most evident when distilled water was employed in rinsing. There was no evident difference in the method of drying the treated samples, and all were found to repel water for several hours, which constituted testing the materials beyond the AATCC Spray Test limits.

The resistance to wetting evaluation of these samples was done by submitting the samples to the Spray Test described as AATCC Standard Test Method 22-1952, which is recommended for measuring the water repellency of fabrics. The results obtained with this method of tests depend primarily on the resistance to wetting or Water repellency of the fibers and yarns in the fabric, and not upon the construction of the fabric. The Spray Ratings by this method were from 50 to 70.

Example 7 A 25 in. x 6 in. sample of 80 x 80 cotton printcloth was padded with a 3.0% beta-ferric oxide hydrosol at room temperature (about 25 C.). The sample was allowed to remain wet with the hydrosol for 3 minutes, then washed thoroughly in distilled water, and hung up to air dry at room temperature.

The sample was then submitted to water repellency test- 4 ing and evaluation as recommended by AATCC Standard Test Method 22-1952. The Spray Ratings were for the treated fabric and 0 for the untreated control.

Example 8 A 10 in. x' 10.5 in. sample of unsized paper towelling was treated by the process of Example 7, and submitted to water repellency testing and evaluation as in Example 7. The results indicated a Spray Rating of 50 for the treated sample, and 3, Spray Rating of 0 for the untreated control.

Example 9 A 6.75 in. x 7.5 in. sample of nitrogenous resin-treated wrapping paper was treated by the process of Example 7, and tested for water repellency in the same manner. The Spray Ratings were 50 for the treated sample and 0 for the untreated control.

Example 10 A 1% Fe O hydrosol was prepared by the process of Example 4, and applied by the process of Example 5 to sized paper, using a distilled water rinse followed by air drying. A 0.3% Fe O add-on was obtained. The test for water repellency was done as in Example 7. The Spray Ratings were 50 for the treated sample, and 0 for the untreated control.

Example 11 To evaluate the shelf-life or effects of storage of the treated cellulosic material, several of the samples which had been stored for 3 years were submitted to water repellency evaluation tests again. The stored and re-tested materials were the following:

(a) Paper towelling which had been treated with a 3.5%

Fe O hydrosol.

(b) Paper towelling which had been treated with a 1% hydrosol to give a 0.3% Fe O add-on.

(c) Cotton printcloth x 80 thread count) which had been treated with a 1.0% Fe O hydrosol.

(d) Cot-ton poplin which had been treated with a 1.0%

Fe O hydrosol.

No loss of water repellency was observed in the re-testing of the stored materials.

I claim: 1. A process for imparting water repellency to cellulosic materials comprising (a) impregnating the cellulosic material with an aqueous cationic beta-iron oxide hydrosol containing about from 1.0% to 3.0% Fe O (b) washing the impregnated material in water, and (c) drying at temperatures about from 20 to C.

References Cited UNITED STATES PATENTS 2,409,630 10/ 1946 Heritage et a1 162-181 X 3,014,835 12/1961 Feigley et a1 162-481 X 3,202,570 8/1965 Videen et a1 162181 X NORMAN G. TORCHIN, Primary Examiner.

I. CANNON. Assistant Examiner. 

1. A PROCESS FOR IMPARTING WATER REPELLENCY TO CELLULOSIC MATERIALS COMPRISING (A) IMPREGNATING THE CELLULOSIC MATERIAL WITH AN AQUEOUS CATIONIC BETA-IRON OXIDE HYDROSOL CONTAINING ABOUT FROM 1.0% TO 3.0% FE2O3, (B) WASHING THE IMPREGNATED MATERIAL IN WATER, AND (C) DRYING AT TEMPERTURES ABOUT FROM 20* TO 100*C. 